Most turbines include a shaft that extends from a hub of a turbine wheel to a shaft bearing. For example, turbines for internal combustion engines typically include a turbine wheel housing that directs exhaust of an engine to a turbine wheel and another housing that houses a bearing for a shaft coupled to the turbine wheel. In such an arrangement, the bearing exists in a lubricant environment that lubricates the bearing to reduce frictional forces, dampen vibration, etc., to thereby allow for high speed operation of the turbine, and the turbine wheel exists in an exhaust environment typically characterized by high temperatures, high pressures and, depending on nature of the exhaust, corrosive reaction chemistry. To separate these two environments, a variety of seal mechanisms have been proposed and used.
In general, such seal mechanisms aim to reduce flow of exhaust to the lubricant environment and/or flow of lubricant to the exhaust environment, both of which can be detrimental to performance (e.g., efficiency, emissions, longevity, etc.). Flow of exhaust to the lubricant environment is usually referred to as “blowby” and flow of lubricant to the exhaust environment is usually referred to as “leakage”. Blowby typically occurs during high speed operation or load where a significant positive pressure differential exists between the exhaust environment and the lubricant environment.
Leakage typically occurs during low turbine-power modes of operation, such as at engine idle, where the pressure differential is negative and/or minimal and insufficient to overcome capillary or other lubricant transport forces.
As the turbomachinery industry trends toward increased turbine inlet pressures, more stringent emission regulations, closed-crankcase ventilation systems, and increased customer sensitivity to the passage of exhaust gas through the turbine seal, a need for seal mechanisms that reduce blowby and/or leakage will increase, and the design of such mechanisms will become more challenging. Various exemplary seal mechanisms disclosed herein aim to reduce blowby and/or leakage. Further, various exemplary seal mechanisms may allow for increased performance (e.g., efficiency, emissions, longevity, etc.), assembly and/or disassembly of turbomachinery.